Ms. Wasserman Schultz was widely criticized during the Democratic primary by supporters of Bernie Sanders of using her position at the DNC to tip the race toward Mrs. Clinton. At least some of that was confirmed at the weekend by the release by Wikileaks of internal DNC emails, which forced her to announce her resignation Sunday.

But in a reaction statement to reporters Sunday, Mrs. Clinton gave Ms. Wasserman Schultz a soft landing by announcing that she would join the Clinton campaign.

“I am glad that she has agreed to serve as honorary chair of my campaign’s 50-state program to gain ground and elect Democrats in every part of the country,” Mrs. Clinton said in the statement.